D.C. Mun. Regs. tit. 9, r. 9-305
All real property shall be assessed on an annual basis.
For the purposes of this chapter, the term "real property" means real estate identified by plat on the records of the District of Columbia Surveyor according to lot and square, together with improvements on that real estate.
For the purposes of this chapter, except where specifically provided otherwise, the word "assess" means to value real property for tax purposes.
For the purposes of this chapter, except where specifically provided otherwise, the word "assessment" means a real property valuation established by the Deputy Chief Financial Officer for tax purposes against which the rate of tax is applied to arrive at the tax liability.
For the purposes of this section, the terms "assess" and "assessed" do not include changes in assessed value resulting from new construction, additions to existing structures, damages to or destruction of property, and any other similar changes specified in D.C. Code §§ 47-829 and 47-830 (1981 Ed.).
D.C. Mun. Regs. tit. 9, r. 9-305